Radio base station, relay station and radio communication method

ABSTRACT

A relay station that includes a receiver configured to receive a signal sequence indicating a connection request, the signal sequence being selected from a predetermined signal sequence group which is used by a plurality of radio terminals, and to measure reception quality; and a control circuit configured to generate a ranging request message indicating that a radio terminal requesting connection exists when determining that adjustments are not necessary based on the reception quality; and a transmitter configured to transmit the ranging request message to a radio base station.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.11/892,425, filed Aug. 22, 2007, now pending, which is a continuation ofJapanese Patent Application No. 2006-301214, filed Nov. 7, 2006, thecontents of each are herein wholly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio base station, a relay station,using radio communication, and a radio communication method. The presentinvention is especially advantageous when it is applied to a case wherea radio communication system prescribed by IEEE802.16 is used as a basesystem and thereto a relay station is added.

2. Description of the Related Art

A radio communication system carrying out communication with the use ofa radio channel, i.e., WCDMA, CDMA2000 or such, as a typical example,currently spreads worldwide. In such a radio communication system, aplurality of radio base stations are set for a service area, and eachradio terminal carries out communication with another communicationapparatus (i.e., another communication terminal) with the use of any ofthe radio base stations. At this time, an overlapping area is providedwith an adjacent service area in which an adjacent base station cancarry out radio communication, and, handover to the adjacent radio basestation is available when a radio environment degrades.

Further, as a radio communication method, for example, code divisionmultiplexing, time division multiplexing, frequency divisionmultiplexing, OFDMA or such, is applicable. In these methods, generallyspeaking, a plurality of radio terminals can connect to a single radiobase station simultaneously.

However, even within the service area in which the radio base stationcan carry out radio communication, high speed communication may not beavailable in a place close to the area boundary, since the radioenvironment may not be satisfactory. Further, even within the area,radio signal propagation may be obstructed by a cause such as a buildingshade. Thus, an area (so-called dead zone) in which satisfactory radioconnection with the radio base station is difficult may occur.

In order to solve the problem, a plan in which a relay station isdisposed in the service area of the radio bases station, and radiocommunication is available between the radio terminal and the radio basestation with the use of the relay station, has been proposed.

Especially, in a task group of 802.16j, introduction of such a relaystation (RS) is currently studied.

As to the above-mentioned IEEE802.16, details are disclosed in, forexample, IEEE Std 802.16TM-2004 and IEEE Std 802.16eTM-2005.

SUMMARY OF THE INVENTION

In the related art described above, the radio terminal can carry outradio communication with the base station directionally or with the useof the relay station. In this case, it is necessary to determine how theradio terminal utilizes the relay station.

An object of the present invention is to provide a system and aprocedure for efficiently utilizing the relay station.

Another object of the present invention is to prevent management of theradio terminal by the radio base station from being obstructed by theexistence of the relay station.

Further another object of the present invention is to preventdegradation in the transmission efficiency otherwise degrading due to afact that a radio communication environment between the radio basestation and the relay station may not necessarily equal to that betweenthe relay station and the radio terminal.

Other than these objects, advantages which may be obtained fromrespective configurations of preferred embodiments described later,which are not obtained from the related art, may be regarded as furtherobjects of the present invention.

(1) According to the present invention, a relay station is used, whichhas:

a reception unit receiving a signal sequence indicating a connectionrequest, from a predetermined signal sequence group;

a control unit generating a ranging request message indicating that aradio terminal newly requesting connection exists; and

a transmission unit transmitting the ranging request message to a radiobase station.

(2) Further, according to the present invention, a radio base station isused, which has:

a reception unit receiving a ranging request message, transmitted from arelay station in response to reception of a signal sequence indicating aconnection request from a radio terminal;

a control unit determining in response to the reception whether or notconnection with the radio terminal is to be newly permitted, andgenerating a ranging response message including the determinationresult; and

a transmission unit transmitting the ranging response message to therelay station.

(3) Further, according to the present invention, a relay station isused, which has:

a reception unit receiving a signal sequence indicating a connectionrequest, from a predetermined signal sequence group;

a control unit generating reception information of the signal sequencereceived by the reception unit or correction value informationindicating a deviation from a predetermined criterion calculated uponthe reception of the reception unit; and

a transmission unit transmitting the reception information or thecorrection value information to a radio base station.

(4) Further, according to the present invention, a relay station isused, which has:

a reception unit receiving a first ranging request message including anidentifier of a radio terminal, from the radio terminal;

a control unit generating in response to the reception a second rangingrequest message including the identifier of the radio terminal; and

a transmission unit transmitting the second ranging request message to aradio base station.

(5) Preferably, the identifier included in the second ranging requestmessage may be stored in a payload or a header.

(6) Further, according to the present invention, a radio base station isused, which has:

a reception unit receiving from a relay station a ranging requestmessage;

a control unit storing identification information of a radio terminalincluded in the ranging request message, and generating a rangingresponse message corresponding to the ranging request message; and

a transmission unit transmitting to the relay station the rangingresponse message.

(7) Preferably, the control unit may include in the ranging responsemessage a connection identifier allocated to the radio terminal; and

the connection identifier is stored with a correspondence to theidentifier of the radio terminal.

(8) Further, according to the present invention, a radio communicationmethod is used, which has the steps of:

in a relay station, receiving a first ranging request message includingan identifier of a radio terminal, from the radio terminal, generating asecond ranging request message to which the identifier of the radioterminal is added, and transmitting the second ranging request messageto a radio base station; and

in the radio base station, receiving the second ranging request message,storing the identifier of the radio terminal included in the secondranging request message, generating a ranging response messagecorresponding to the second ranging request message, and transmittingthe ranging response message to the relay station.

(9) Further, according to the present invention, a radio communicationmethod is used, which has the steps of:

in a relay station, receiving a signal sequence indicating a connectionrequest from a radio terminal, generating a ranging request messageindicating that the radio terminal newly requesting connection exits,and transmitting the ranging request message; and

in a radio base station, receiving the ranging request message,determining whether or not to newly permit a connection of the radioterminal, generating a ranging response message including thedetermination result, and transmitting the ranging response message.

(10) Preferably, the ranging request message may be transmitted to theradio base station when the reception of the signal sequence meets apredetermined criterion, and may not be transmitted when thepredetermined criterion is not met.

(11) Further, according to the present invention, a radio communicationmethod is used, which has the steps of:

in a relay station, receiving a signal sequence indicating a connectionrequest from a radio terminal; and

in the relay station, determining whether or not to newly permitconnection with the radio terminal, generating a ranging responsemessage including the determination result, and transmitting the rangingresponse message to the radio terminal.

(12) Further, according to the present invention, a relay station isused, which has:

a reception unit receiving a signal sequence indicating a connectionrequest from a radio terminal;

a control unit determining whether or not to newly permit connectionwith the radio station, and generating a ranging response messageincluding the determination result; and

a transmission unit transmitting the ranging response message to theradio terminal.

(13) Further, according to the present invention, a radio base stationis used, which has:

a control unit generating key information used for communication betweena radio terminal and the radio base station; and

a transmission unit transmitting the key information to the radioterminal and a relay station.

(14) Preferably, the key information may include a shared key and anauthentication key.

(15) Preferably, the control unit may transmit the key information afterencrypting it with such a key that the relay station can decrypt it.

(16) Further, according to the present invention, a relay station isused, which has:

a reception unit receiving a message transmitted from a radio basestation;

a processing unit modifying data obtained from decrypting encrypted datatransmitted between a radio terminal and the radio base station, withkey information included in the message; and

a transmission unit transmitting the thus-modified data.

(17) Preferably, the key information may include shared key information,and the data transmitted by the transmission unit may include dataobtained from encryption with the use of the shared key informationafter the modification.

(18) Further according to the present invention, a relay station isused, which has:

a reception unit receiving a message transmitted from a radio basestation;

a processing unit modifying data to which authentication data is added,transmitted between a radio terminal and a radio base station, andadding the authentication data to the thus-modified data with the use ofauthentication key information included in the message; and

a transmission unit transmitting the data to which the authenticationdata is added by the processing unit.

According to the present invention, it is possible to provide the systemand the procedure in which the relay station can be efficiently used.

Further, according to the present invention, management of the radioterminal by the radio base station can be made smoothly even with theexistence of the relay station.

Further, according to the present invention, it is possible to preventdegradation in the transmission efficiency otherwise degrading due to afact that a radio communication environment between the radio basestation and the relay station may not necessarily equal to that betweenthe relay station and the radio terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of the present invention will becomemore apparent from the following detailed description when read inconjunction with the accompanying drawings:

FIG. 1 shows an example of a ranging and basic capability registrationsequence;

FIG. 2 shows a processing flow of a RS when receiving a ranging codefrom a MS;

FIG. 3 shows a processing flow of a RS when receiving a ranging requestfrom the MS;

FIG. 4 shows a processing flow of the RS when receiving a rangingresponse from the BS;

FIG. 5 shows a processing flow of the BS when receiving a rangingrequest;

FIG. 6 shows a block configuration example of the BS;

FIG. 7 shows a management table of the MS (1);

FIG. 8 shows a block configuration example of the RS;

FIG. 9 shows another example of the ranging and basic capabilityregistration sequence;

FIG. 10 shows a processing flow of the RS when receiving a ranging codefrom the MS;

FIG. 11 shows a processing flow of the RS when receiving a rangingrequest from the MS;

FIG. 12 shows a processing flow of the RS when receiving a rangingresponse from the BS;

FIG. 13 shows a processing flow of the BS when receiving a rangingrequest;

FIG. 14 shows another block configuration example of the RS; and

FIG. 15 shows an example of an authentication sequence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to figures, embodiments of the present invention will bedescribed. It is noted that, although separate embodiments aredescribed, for the sake of convenience, they may be combined and thus,with advantages from the combination, the advantages may be furtherimproved.

[a] Description of First Embodiment

In a first embodiment of the present invention, a relay stationtransmits a signal after processing a signal received from a radioterminal, to a radio base station.

In this configuration, the relay station positively functions incommunication between the radio terminal and the radio base station. Forexample, a signal which is not necessarily required to be transmitted tothe radio base station is not transmitted to the radio base station.Thus, management of the radio terminal by the radio base station can becarried out smoothly. Further, signal processing which can be carriedout by the relay station is carried out by the relay station itself.Accordingly, it is possible to reduce a processing load of the radiobase station. Further, the radio base station can manage as to whichrelay station is used by the radio terminal.

“Basic System Configuration”:

FIG. 1 shows a processing sequence for a case where the relay station isnewly introduced to a radio communication system prescribed inIEEE802.16, as one example of a radio communication system including theradio base station and the radio terminal for carrying out radiocommunication. This sequence may also be applied to another type ofradio communication system.

First, a basic function of each apparatus will be described.

In FIG. 1, a BS (Base Station) 300 denotes a radio base station, whichis one of radio base stations disposed in an area in which the presentradio communication system provides a radio communication service.Accordingly, there are other radio base stations providing other radioareas, which are not shown, adjacent to the area provided by the presentradio base station.

In this radio communication system, transmission/reception channels(i.e., uplink and downlink channels) of an MS 100 and an RS 200 arecontrolled by transmission/reception channel definition data, called MAPdata.

The MAP data includes, for example, transmission/reception timing,sub-channel information used for transmission/reception, code valuesindicating a modulation method and an error correction coding method,and a CID (Connection ID). The MS 100 and the RS 200 determine whetheror not connection is relevant to themselves, from the CID, and, carryout radio communication (transmission or repetition of a radio signal)in the transmission/reception timing, with the sub-cannels correspondingto the CID. Accordingly, it may be said that the MAP data defines atransmission/reception region. It is noted that, data of the MAP data,defining the communication region of the uplink direction (from the MS100 to the RS 200 (or the BS 300), is referred to as UL (Up Link)-MAPdata, while data of the MAP data, defining the communication region ofthe downlink direction (from the BS 300 to the RS 200 (or the MS 100)),is refereed to as DL (Down Link)-MAP data.

The MS 100 denotes a radio terminal, which exists in the radio areaprovided by the BS 300, and thereby, can communicate with the BS 300. Itis noted that the radio terminal is allowed to carry out communicationwith changing a location (for example, upon moving). Then, when it movesto under another base station providing adjacent another radio area,handover processing is carried out and thereby, radio communication canbe continued. The MS 100 can communicate directly with the BS 300.However, in this example, the MS 100 carries out radio communicationwith the BS 300 with the use of the RS 200.

The RS 200 denotes a relay station, which is disposed so that it cancommunicate with the BS 300, transmits a signal to the MS 100 based on asignal received from the BS 300, or, reversely, transmits a signal tothe BS 300 based on a signal received from the MS 100, whereby theabove-mentioned dead zone can be eliminated.

“Ranging and Basic Capability Registration”:

Next, with reference to FIG. 1, a ranging and basic capabilityregistration sequence for starting connection of the radio terminal withthe radio base station will be described. FIG. 1 shows processing forwhen so-called network entry is carried out.

It is noted that both the BS 300 and the RS 200 generate the MAP data,respectively, and transmit the same. That is, the BS 300 transmits theMAP data for defining a transmission/reception region of radiocommunication with the MS 100 belonging thereto and with the RS 200 withwhich radio communication is directly carried out. Further, based on thedata to transmit/receive, the BS 300 carries out scheduling, andgenerates the MAP data according to the scheduling.

The RS 200 generates the MAP data based on scheduling for defining atransmission/reception region of radio communication with the MS 100belonging thereto, and transmits the same.

The transmission/reception region defined by the MAP data of the BS 300and the transmission/reception region defined by the MAP data of the RS200 are separated by timing, by frequencies, by spread codes or such,and thus, have such a relationship that radio communication can becarried out without obstruction to one another.

In FIG. 1, (1), the RS 200 transmits a known signal (i.e., a preamblesignal) as a synchronization signal. Then, subsequent to the preamblesignal, MAP data (including both UL- and DL-MAP data) is used. Also,user data is transmitted from the RS 200 in the transmission regiondefined by the DL-MAP data, to the MS 100 (2).

The MS 100 receives the preamble signal thus transmitted by the RS 200,and establishes synchronization to a radio frame which the RS 200 hastransmitted. It is noted that, the MS 100 should not distinguish betweenthe RS 200 and the BS 300. This is because, the processing for detectingthe preamble signal and subsequently carrying out transmission/receptionaccording to the MAP data may be the same between the case of radiocommunication with BS 300 and the radio communication with the RS 200.

The MS 100 receives MAP data (DL and UL) based on the preamble (2),detects the transmission region defined by the MAP data, and receivesDCD and UCD transmitted through the transmission region. It is notedthat the DCD and the UCD are data broadcasted, and thus, BC which is abroadcast connection ID is stored in the definition information of thetransmission region in the DL-MAP data and in the transmission region.In the figures, BC, IR, Bms and Brs, provided at a top of each message,denote the connection IDs used for transmission. That is, BC, IR, Bmsand Brs denote a broadcast CID, an initial ranging CID, a MS's basic CIDand a RS's basic CID, respectively.

As a function of the DCD (Downlink Channel Descriptor), it defines arelationship between code values DIUC (Downlink Internal Usage Code)indicating a downlink modulation method and an error correction encodingmethod (including an encoding rate), and the downlink modulation methodand the error correction encoding method (including an encoding rate)themselves. For example, DIUC=3 may define 16QAM, a convolution code andan encoding rate of 3/4. Thereby, merely by defining DIUC=3 in theDL-MAP, it is possible to notify the RS 200 or the MS 100 that theregion is encoded and modulated by 16QAM, the convolution code and theencoding rate of 3/4. Similarly, UCD (Uplink Channel Descriptor) definesa relationship between code values UIUC (Uplink Internal Usage Code)indicating an uplink modulation method and an error correction encodingmethod (including encoding rate), and the uplink modulation method andthe error correction encoding method (including encoding rate)themselves.

Thus, by receiving the definitions of DIUC and UIUC from DCD and UCD, itbecomes possible that the MS 100 or RS 200 can interpret the DL-MAP orUL-MAP. The MS 100 obtains the transmission region by which transmissionof a ranging code indicating a request for connection of the MS 100 isallowed, by receiving the UL-MAP data in (2) or by receiving the UL-MAPdata included in the subsequent frame (3). The ranging region is aregion for transmitting a predetermined signal (i.e., a CDMA rangingcode) from the MS 100. The RS 200 notifies of this region to the MS 100with the MAP data. The ranging region may be one including a pluralityof regions, for example, and thus, such a manner is allowed that a firstMS transmits a predetermined signal in a first region while a second MStransmits a predetermined signal in a second region.

As the CDMA ranging code (i.e., a signal sequence), for example, it ispreferable to selectively use, from a predetermined number or pluralityof codes (i.e., a signal sequence group). For example, upon transmissionof a code, the MS 100 selects one of the plurality of codes, andtransmits the same. Upon the selection, it is possible to reduce apossibility that the same code is selected, even when a plurality of MSsshare the codes, when the code is selected randomly.

After obtaining the transmission region for the ranging signal, the MS100 selects any of the regions (for example, a first region) from amongthe ranging regions, and transmits the selected CDMA code (for example,a code 1) in the selected region (4).

The CDMA ranging code is a CDMA code for initial ranging. On the otherhand, when the MS 100 comes from another BS 300 in a handover manner, aCDMA code for HO ranging is transmitted.

The RS 200 receives the CDMA ranging code transmitted in thetransmission region of the ranging signal, and stores the code receptioninformation such as the reception timing (for example, which region isused), a type of the code (in this example, the code 1, mentioned above)and so forth. Further, other than the code reception information, adeviation of the frequency (sub-band) upon the code reception from astandard frequency, a deviation of the reception power from a standardreception power, a deviation of the reception timing from standardtiming (i.e., the transmission region of the ranging region defined bythe MAP data) and so forth are measured, and are stored as correctionvalues (i.e., correction values of transmission parameters of the MS100).

Then the RS 200 transmits an RNG-REQ message to the BS 300 (5).

As transmission timing of the RNG-REQ message, a region in which datatransmission is possible from the RS 200 to the BS 300, defined by theUL-MAP transmitted by the BS 300, is used. That is, a communication link(MMR link) using the data transmission/reception region between the BS300 and the RS 200, defined by the BS 300, is used. However, in thiscase, the MMR link in the uplink direction is used. Further, as to theMMR link, different regions should be preferably designated torespective RSs, for the purpose of avoiding collision.

As the contents of the RNG-REQ message, a message requesting ranging maybe used. Specifically, a basic CID of the RS 200 as a connection ID (forexample, a CID, designated by the BS 300, which is an ID fordistinguishing from the radio terminal and the other relay stationsbelonging to the BS 300, i.e., Brs) may be used, and the message mayinclude data (i.e., New MS) for notifying that entry of a new MS 100 ismade (i.e., a new MS 100 exists which requests connection).

It is preferable that the above-mentioned New MS is data (i.e., thenumber) which is changed (incremented) each time the RNG-REQ messageincluding New MS is transmitted. For example, when the RS 200 receivesthe code 1 in the first region of the ranging region, subsequentlyreceives a code 2 in the second region, and transmits RNG-REQ messagesfor the respective codes, the transmission may be made with such asetting of SN=1, and then, SN=2, respectively.

The example of the contents of the message transmitted in (5) has beenthus described. Preferably, this message may be transmitted to the BS300 when the deviations of the frequency, the reception power level andthe timing upon the code reception lie within predetermined ranges(i.e., no correction is required; a “success” status). Otherwise, themessage may not be transmitted to the BS 300. This is because, when theerror is large, the MS 100 should be made to again transmit the CDMAcode, then the RNG-REQ message should be generated based on there-transmitted CDMA code, and, should be transmitted to the BS 300.Thus, it is possible to reduce messages to be transmitted to the BS 300,and thus, the processing load of the BS 300 can be reduced.

The BS 300 receiving the RNG-REQ can determine from the CID the relaystation which has thus transmitted the message. Then, since the messageindicates that the entry of the new MS 100 is made, the BS 300 refers tothe communication resources of the BS 300 itself (i.e., radio channels,radio communication units and so forth), RS busy resource conditions andso forth, which are separately managed and stored, and, determineswhether or not the new MS 100 can be accepted.

The determination result is then transmitted to the RS 200 as a RNG-RSPmessage (6). The transmission region to be used there is the MMR linkdefined by the MAP data of the BS 300 described above. As the CID, Brscan be used.

In this RNG-RSP message, for example, a “success” status may be includedwhen the MS 100 can be accepted, while an “abort” status may be includedwhen the MS 100 cannot be accepted. If necessary, the New MS, the sameas the New MS in the RNG-REQ received from the RS, may be furtherincluded.

The RS 200 has having received the RNG-RSP message from the BS 300continues the ranging processing of the MS 100 when the status thusnotified of is “success”. That is, when a correction is required for thereception frequency, the reception power level and the reception timingof the ranging code which the RS 200 has received, the RS 200 transmitsRNG-RSP (“continue” status) as a response message including thecorresponding correction values.

The correction values are those obtained upon the reception of theranging CDMA code, which is stored in the above-mentioned example. Inorder to search for the correction values, the New MS may be used as asearch key when the correction values are stored with correspondence tothe New MS. Any other identification information may also be used as asearch key.

When no correction is required, the RS 200 transmits RNG-RSP (“success”)as a response message (7).

On the other hand, when the status notified of from the BS 300 is“abort”, the RS 200 transmits to the MS 100, RNG-RSP of an “abort”status. The MS 100 which has thus received the RNG-RSP of the “abort”status stops the connection processing for the RS 200, and then,inquires into another BS or another RS. That is, the MS 100 tries toreceive another preamble.

It is noted that, in such a case that the BS's resources are sufficient,the RS 200 may omit the step of transmitting the RNG-REQ to the BS 300notifying existence of the MS 100 which requests connection, in responseto the reception of the ranging code. That is, thetransmission/reception with the BS 300 in (5), (6) may be omitted, andRNG-RSP (“continue” status) or RNG-RSP (“success” status) may betransmitted in (7). Thereby, an increase in the processing speed can beachieved. The BS 300 may notify the RS 200 of the number of MSs whichcan be processed through the MMR link, and the RS 200 may omit theprocessing as mentioned above, when this number is not actuallyexceeded.

It is noted that the RNG-RSP message is transmitted in the transmissionregion which is made to have correspondence to IR (Initial Ranging) as aconnection ID in the DL-MAP data. The IR may be used as one unique IDused for ranging processing. At this time, since RNG-RSP can be receivedby all the radio terminals which have transmitted the CDMA ranging code,it is preferable that the reception information of the CDMA ranging codeis stored in the RGN-RSP message, and thus the transmission destinationof the RNG-RSP is specified. It is noted that, in the examples mentionedbelow, the RS 200 stores the reception information of the CDMA rangingcode, search may be made with the New MS or such which may be used as akey, and, the thus-obtained reception information may be transmitted.

The MS 100 having received the RNG-RSP adjusts the frequency,transmission power and timing according to the correction valuesincluded in the RNG-RSP when the status is “continue”, and again, the MS100 transmits a ranging CDMA code to the RS 200 (not shown). When thestatus is “success”, the MS 100 receives the CDMA allocation IE includedin the UL-MAP data included in the same frame or a subsequent frame.

As the CDMA allocation IE included in the UL-MAP data, BC is used as aconnection ID. Therefore, all the radio terminals belonging to the RS200 can receive it. Accordingly, the MS 100 carries out matching thetype of the code (code 1) and the timing (region 1) which the MS 100itself has transmitted, with the reception information of the codestored in the CDMA allocation IE. Then, when the matching results inagreement, the MS 100 receives it as a message transmitted for itself,and detects the transmission region defined by the CDMA allocation IE.On the side of RS 200, a correspondence relationship between thetransmission region which the RS 200 has allocated and theidentification information of the MS 100 such as New MS or such, isstored.

The MS 100 who thus has received the CDMA allocation IE transmitted foritself, transmits an RNG-RSP message including the MAC address (MSID)which is identification information for the MS 100, to the RS 200 viathe transmission region detected as mentioned above (9). It is notedthat, as a connection ID, the IR is used, which is also stored in theRNG-RSP message.

When receiving the RNG-RSP message designated by the CDMA allocation IEvia the transmission region, the RS 200 specifies the New MScorresponding to the transmission region, and, generates and transmitsan RNG-REQ message to the BS 300.

In this stage, the identification information (MSID) of the MS 100 hasbeen obtained. Accordingly, as a result of the MSID being included inthe RNG-REQ message, it can be seen that the RNG-REQ message transmittedby the RS 200 corresponds to a ranging request from the MS 100.Preferably, the New MS should be further included there.

The RS 200 adds Brs which is the basic CID of the RS 200 to theinformation to obtain the RNG-REQ message, and transmits the same to theBS 300 via the MMR link (10).

When receiving the RNG-REQ message from the RS 200, the BS 300identifies the RS 200 which has transmitted the message, from the CID(Brs) included in the header thereof. Further, the BS 300 stores the MACaddress of the MS 100 (MSID) included in the payload part, withassociation to the RS 200. Thereby, the BS 300 can manage as to which RSthe MS 300, identified by the MSID, belongs to. From the New MS includedin the RNG-RSP, it is possible to check whether or not the MS, the sameas the MS for which the status “success” has been given in (5), (6), hastransmitted the RNG-REQ. When the New MS does not correspond to the MS100, from which the message has been received (5), the subsequentprocessing may be rejected and the current processing may be terminated.

The BS 300 having received the RNG-RSP message further creates a basicCID and a primary CID for the MS 100, adds the MSID, and thus, generatesan RNG-RSP message, which is then returned to the RS 200. At this time,as a connection ID, Brs may be used. Then, with the use of the MMR link,the same as the above, the RNG-RSP message is transmitted via the dataregion (11).

The RS 200 which has thus received the RNG-RSP message including thebasic CID and the primary CID for the MS 100, from the BS 300, convertsthe connection ID in the header into IR, and transfers the RNG-RSPmessage, having been thus converted, to the MS 100 (12). It is notedthat the connection ID is stored in the DL-MAP data together with thedefinition information of the corresponding data transmission region,and also, it is stored in the header part of the data stored in thetransmission region.

Based on IR which is the connection ID of the DL-MAP data, the MS 100receives the corresponding data transmission region, and then, the MS100 receives the RNG-RSP message including the basic CID and the primaryCID. Since the MSID is also stored, the MS 100 can easily determine thatthe message is one for itself.

After that, the MS 100 carries out processing for notifying of acapability of itself.

That is, with the use of the thus-obtained basic CID as the connectionID, the MS 100 transmits an SBC-REQ message to the RS 200. That is, theSBC-REQ message (including the basic CID) is transmitted via thetransmission region designated as a region for transmission by theUL-MAP data (13).

The RS 200 having received the SBC-REQ message transfers the same withthe basic CID of the MS 100 used as it is, to the BS 300 via the MMRlink (14).

The BS 300 having received the SBC-REQ message generates an SBC-RSPmessage notifying the MS 100 of a function, from among those of thecapability of the MS 100, thus notified of from the MS 100, which eachof the MS 100, RS 200 and BS 300 can support. The SBC-RSP message isthen transmitted to the RS 200 via the MMR link (15). At this time, thebasic CID of the MS 100 is used as the connection ID. It is noted that,the contents which are thus notified of, are stored with correspondenceto the MS 100, on the side of the BS 300.

Brs may also be used as the connection ID for the MMR link. In thiscase, it is preferable that information for identifying the MS 100 isstored in the message. As the information to store, for example, MSID,the basic CID of the MS 100 or such, may be used. From the information,the BS 300 can identify the MS 100, and thus, can identify the MS forwhich the capacity to use is determined. As another method, it is alsopossible to carry out transmission/reception ((14), (15)) of themessages using the MMR link with the use of another CID corresponding,in a one-to-one manner, to the basic CID of the MS 100.

The RS 200 transfers the SBC-RSP to the MS 100 (16). The basic CID maybe used as the connection ID.

Thus, the ranging and basic capability registration sequence has beendescribed. Thereby, the reception information of the code should not betransmitted to the BS 300. Thus, it is possible to prevent degradationin the channel efficiency. Further, management of the MS 100 by the BS300 can be carried out easily.

It is noted that, in the process of relaying the messages between the MS100 and the BS 300, the RS 200 may obtain the information included inthe messages and store the same.

Thereby, not only the BS 300 but also the RS 200 can manage the MACaddress (MSID) of the MS 100, the basic CID, the primary CID, and thesupport functions notified by the SBC-REQ and SBC-RSP messages.

Thereby, the RS 200 can properly select the modulation method and theerror correction encoding method supported by the MS. Also, the RS 200may transmit the stored contents in response to a query from the BS 300.Thus, the RS 200 can function as a backup apparatus.

“Processing Flow in RS, BS”:

Next, processing flows in each apparatus will be described.

FIG. 2 shows a processing flow of the RS 200 upon receiving the rangingcode from the MS 100; FIG. 3 shows a processing flow of the RS 200 whenreceiving the RNG-REQ from the MS 100; FIG. 4 shows a processing flow ofthe RS 200 when receiving the RNG-RSP from the BS 300; and FIG. 5 showsa processing flow of the BS 300 when receiving the RNG-REQ.

Processing Flow of the RS 200 when Receiving the Ranging Code From theMS 100 (FIG. 2):

This processing flow is carried out by a control part of the RS 200.

The RS 200 determines whether or not to have received the ranging codefrom the MS 100 (S1). When the determination result is No, the RS 200carries out subsequent reception again (S1). When the result is Yes, theRS 200 determines the status of code reception (S2). When the status is“success” (Yes), the RS 200 generates an RNG-REQ message includinginformation “New MS” indicating that a new MS connection request exists(S3), and transmits the same to the BS 300 with the basic CID of the RS200 added in the CID field of the header (S4).

When the result of S2 is No (not “success”), the RS 200 transmits anRNG-RSP message to the MS 100, including a status “continue” (S5). Atthis time, initial ranging (IR) is used as the CID.

Processing Flow of the RS 200 when Receiving the RNG-REQ from the MS 100(FIG. 3):

This processing flow is mainly carried out by the control part of the RS200.

The RS 200 determines whether or not to have received the RNG-REQ fromthe MS 100 (S11). When the result is No, next reception check is carriedout (S11). When the result is Yes, it is determined whether or not theCID is IR (S12). When the result is No, periodic ranging processing ofthe MS 100 is carried out (S15). That is, instead of initial rangingbeing carried out first, a signal for correcting errors in thetransmission power, the transmission timing, the transmission frequencyand so forth, is generated, as ranging processing which should becarried out periodically after that, and the signal is transmitted tothe MS 100.

When the result of S12 is Yes, the RS 200 converts the CID of the headerof the received RNG-REQ message into the basic CID of the RS 200, andtransmits the RNG-REQ message to the BS 300 (S13, S14). New MS may alsobe included in the message.

Processing Flow of the RS 200 when Receiving the RNG-RSP from the BS 300(FIG. 4):

This processing flow is mainly carried out by the control part of the RS200.

First, the RS 200 determines whether or not to have received the RNG-RSP(S21). When the result is No, next reception check is carried out again(S21). When the result is Yes, the RS 200 determines whether or not theCID is other than the IR (S22). When the result is the IR (No), the RS200 carried out initial ranging processing of the RS 200 (S26).

When the result of S22 is Yes (for example, the CID is Brs), it isdetermined whether or not a “New MS” flag exists (S23). When the resultis No, it is determined whether or not MSID exists (S25). When MSIDexists (Yes), the CID of the header of the RNG-RSP is changed into theIR, and the RNG-RSP is transmitted to the MS 100 (S29). When MSID doesnot exist (No in S25), the RS 200 adjusts the frequency, transmissionpower and timing according to the correction information included in theRNG-RSP, as periodic ranging processing of the RS 200 itself (S30).

On the other hand, when the “New MS” flag exists (Yes in S23), it isdetermined whether or not the status is “success” (S24). When the statusis “success” (Yes), the RNG-RSP including the status “success” isreturned to the MS 100 (S28). When the status is other than “success”(No in S24), the RNG-RSP including of a status “abort” is returned tothe MS 100 (S27).

Processing Flow of the BS 300 when Receiving the RNG-REQ (FIG. 5):

This processing flow is carried out mainly by a control part of the BS300.

First, the BS 300 determines whether or not to have received the RNG-REQ(S41). When the result is No, the BS 300 carries out next receptioncheck again (S41). When the result of S41 is Yes, it is determinedwhether or not the CID is other than the IR (S42). When the result is No(i.e., the CID is the IR), the BS 300 carries out initial rangingprocessing of the MS 100 or the RS 200 which the BS 300 communicateswith directly (S52).

When the CID is other than the IR (Yes in S42), it is determined whetheror not the CID is the basic CID of the RS 200 (S43). When the result isNo, the BS 300 carries out periodic ranging processing of the MS 100(S48).

When the CID is the basic CID of the RS 200 (Yes in S43), it isdetermined whether or not a “New MS” flag exits (S44). When the “New MS”flag exists (Yes), it is determined whether or not the new MS 100 can beaccepted (S46). When it can be accepted (Yes), the BS 300 generates anRNG-RSP including a status “success”, and transmits the RNG-RSP to theRS 200 with the use of the same CID as that of the RNG-REQ (S50). Whenthe new MS 100 cannot be accepted (No in S46), the BS 300 generates anRNG-RSP including a status “abort”, and transmits the RNG-RSP to the RS200 with the use of the same CID as that of the RNG-REQ (S51).

When no “New MS” flag exists (No in S44), the BS 300 determines whetheror not the MS MAC address (MSID) exists (S41). When MSID does not exist(No), the BS 300 carries out periodic ranging processing of the RS 200.When MSID exists (Yes in S41), the BS 300 stores the MAC adders (MSID)included in the RNG-REQ, with association to the RS 200 expressed by theCID included in the header of the message (S47). Then, the BS 300generates an RNG-RSP including the basic CID and the primary CID, andtransmits the same to the RS 200 with the use of the same CID as that ofRNG-REQ (S49).

“Configuration of Each Apparatus”:

FIG. 6 shows a block configuration of the BS 300.

In FIG. 6, 10 denotes an antenna for transmission/reception of radiosignals with the RS 200 or the MS 100; 11 denotes duplexer for theantenna 10 to be shared for transmission/reception; 12 denotes areception part; 13 denotes a demodulation part for demodulating thereception signal; 14 denotes a decoding part for decoding thedemodulated reception signal; 15 denotes a control message extractionpart extracting control data from the reception signal to give it to aranging control part 26, and also, transferring data such as user datato a packet reproduction part 16; 16 denotes the packet reproductionpart generating a packet from the data transferred from the controlmessage extraction part 15 to give it to a NW interface part 17.

17 denotes the NW interface part for providing an interface (in thisexample, for packet communication) with a routing apparatus (not shown;which is connected to a plurality of radio base stations, and carriesout data forwarding control); 18 denotes a packet identification part,which identifies an IP address included in packet data received throughthe NW interface part 17, identifies a destination MS 100 based on theIP address (for example, a correspondence between IP address data andthe MS's ID being previously stored, and, ID of the corresponding MSbeing obtained), and also, obtains QoS information corresponding to theID (QoS being also previously stored with correspondence to the ID),gives the QoS information to an MAP information generation part 21 torequest it to allocate a band, and stores the packet data received fromthe NW interface part 17 in a packet buffer part 19.

21 denotes the MAP information generating part which, in response to theband allocation request, determines a communication route by searchingwith the MS's ID as a key (or determines a relay station to use),generates MAP data setting a mapping area according to the QoS in any ofthe downlink data transmission regions, and also, gives instructions toa PDU generation part 20 for configuring a radio frame accordingthereto.

20 denotes the PDU generation part which generates a PDU such that MAPdata and transmission data are stored in respective regions of a radioframe created based on a synchronization signal (preamble), and gives itto an encoding part 22. 22 denotes the encoding part; 23 denotes amodulation part; and 24 denotes a transmission part. The encoding part22 carries out encoding processing such as error correction enclosing orsuch on the PDU data, the modulation part 23 modulates the thus-obtaineddata, and the transmission part 24 transmits the thus-modulated data asa radio signal via the antenna 10.

25 and 26 denote a control message generation part and the rangingcontrol part, respectively, included in the control part of the BS 300which carries out control of the respective parts of the BS 300.

The control part is connected with a storage part, in which varioussorts of data the BS 300 should store is stored. For example, capabilityinformation determined for each MS, information as to whether or not MSshould be directly communicated with, and further, information as towhich RS is used to communicate with MS, and so forth, is stored.Further, the storage part is used for managing busy conditions of the BSand RS resources.

The control message generation part 25 generates various sorts ofcontrol messages according to instructions from the ranging control part26, and gives them to the PDU generation part 20 as transmission data.Further, for the purpose of ensuring transmission regions, a request forensuring the transmission regions is made to the MAP informationgeneration part 21. At this time, also information required for creatingthe MAP data (i.e., connection IDs and so forth) is given to the MAPinformation generation part 21.

26 denotes the ranging control part, which analyses the control message(for example, RNG-REQ) extracted by the control message extraction part15, analyses the CID included in the message header, and requests thecontrol message generation part 25 to generate RNG-RSP and transmit thesame.

When the CID is one for initial ranging (IR), this means a rangingrequest message from the MS or RS belonging to the BS 300. Whencorrection of the frequency, transmission power and timing of MS is notrequired, it is notified to the control message generation part 25 togenerate an RNG-RSP including the MAC address included in the RNG-REQ,the “success” status, the basic CID, the primary CID and so forth, isgenerated, and transmit it with CID=IR.

On the other hand, when the above-mentioned correction is required, itis notified to the control message generation part 25 to generate anRNG-RSP including the MAC address included in the RNG-REQ, the“continue” status and necessary correction information, and transmit thesame with CID=IR.

When the CID is not for IR, but is the basic CID of the MS, periodicranging of the MS is carried out. The same as the above-mentioned caseof the IR, it is notified to the control message generation part 25 togenerate an RNG-RSP including contents according to whether or not thecorrection is required, and transmit the same with the use of the basicCID of the RNG-REQ.

When the CID is not for IR but is the basic CID of the RS, processing tocarry out differs according to whether or not a “New MS” indicatorexists in the payload part of the RNG-REQ message.

When the “New MS” indicator does not exist, processing to carry outdefers according to whether or not the MS MAC address (MSID) exists.When the MS MAC address (MSID) does not exist, periodic rangingprocessing of the RS is carried out. On the other hand, when the MS MACaddress is included, this massage that, the received RNG-REQ is onetransmitted from the MS, and then, is relayed by RS. At this time, theMS MAC address included in the RNG-REQ and the RS's basic CID includedin the header of the RNG-REQ are managed with association to oneanother, so that the RS via which the MS is connected can be identified.Next, it is notified to the control message generation part 25 togenerate an RNG-RSP message including the basic CID and the primary CIDto be allocated to the MS, and transmit it to the RS with the use of thebasic CID of the RS. An MS management table is used to manageassociation between the MS and the RS, and the MS's basic CID and theprimary CID.

FIG. 7 shows an example of the MS management table.

This shows a part of the contents of the above-mentioned storage part.

As shown in FIG. 7, the MS management table manages and storesinformation indicating whether or not communication via the RS iscarried out with correspondence to the MS's MAC address (MSID),information indicating which RS is used when the RS is used, the basicCID and the primary CID.

When the “New MS” indicator exists, it is determined whether or not thenew MS can be accepted. Whether or not the new MS can be accepted can bedetermined from busy conditions of various sorts of resources, such asthe radio resource busy condition, the management table busy condition,and so forth. When the new MS can be accepted, it is notified to thecontrol message generation part 25 to generate an RNG-RSP including a“success” status, and transmit it to the RS with the use of the same CIDas that of the RNG-REQ. On the other hand, when the new MS cannot beaccepted, it is notified to the control message generation part 25 togenerate an RNG-RSP including an “abort” status, and transmit it to theRS with the use of the same CID as that of the RNG-REQ.

FIG. 8 shows a block configuration of the RS 200.

In FIG. 8, 30 denotes an antenna for transmission/reception of radiosignals with the BS or the MS; 31 denotes a duplexer for the antenna 10to be shared for the transmission/reception; 32 denotes a receptionpart; 33 denotes a demodulation part demodulating a reception signal; 34denotes a decoding part decoding the thus-demodulated signal; and 35denotes a control message extraction part which extracts MAP data fromthe decoded data (received from the BS), gives it to a MAP informationgeneration and analysis part 36, and also, transfers data for the MSfrom the BS to a packet buffer part 38. Also the same in a case ofreceiving a radio signal from the MS, reception data is transferred tothe packet buffer part 38 for being transmitted to the BS. Further, thecontrol message extraction part 35 extracts a control message (RNG-REQ,RNG-RSP, or such) from the received message, and gives it to a rangingcontrol part 39.

37 denotes a code reception part which, when receiving a ranging codefrom the MS (initial ranging, handover ranging or such), determineswhether or not correction is required for the frequency, reception powerlevel and timing of the reception signal, and notifies the rangingcontrol part 39 of the status (success/abort/continue), as well asinformation concerning the received code, for example, code receptioninformation such as the frame number, sub-channel, code value and soforth of the reception of the code, together with the correction values.

39, 40 denote the ranging control part and a control message generationpart included in the control part controlling the respective parts ofthe RS 200, respectively.

The control part is connected to a storage part. In the storage part,various sorts of data which the RS 200 should store are stored. Forexample, the code reception information, correction information and soforth are stored.

When receiving information from the code reception part 37, and when thestatus is “success”, the ranging control part 39 notifies the controlmessage generation part 40 to generate an RNG-REQ including a “New MS”indicator, and transmit it to the BS with the basic CID of the RS. Onone hand, when the status is “continue”, it is notified to the controlmessage generation part 40 to generate an RNG-RSP message including thecorrection information and information concerning the code, and transmitit to the MS with the CID for initial ranging.

Further, when the RNG-REQ message is received from the control messageextraction part 35, the ranging control part 39 determines whether ornot the CID included in the header of the message is the CID for initialranging. When it is the CID for IR, it is notified to the controlmessage generation part 40 to change the CID field of the header of thereceived RNG-RSP message into the basic CID of the RS 200, and transmitit to BS. On one hand, when it is not the CID for IR, that is, it is theMS's basic CID, ordinary periodic ranging processing of the MS is thencarried out.

Further, when the RNG-RSP message is received from the control messageextraction part 35, first it is determined whether or not the CID is theCID for initial ranging. When it is the CID for IR, initial rangingprocessing of the RS 200 is carried out. That is, when the MAC addressincluded in the RNG-RSP is the own MAC address, the basic CID and theprimary CID included in the message are stored, which are then used forsubsequent transmission/reception of control messages. On the otherhand, when it is other than the CID for IR, processing to carry outdiffers according to whether or not the message includes a “New MS”indicator. When the “New MS” indicator is included, and also, when a“success” status is included in the message, it is notified to thecontrol message generation part 40 to generate an RNG-RSP messageincluding a “success” status, and return it to the MS with a CID for IR.However, when no “success” status is included, it is notified to thecontrol message generation part 40 to generate an RNG-RSP messageincluding an “abort” status, and return it to the MS with a CID for IR.On one hand, when no “New MS” indicator is included, and when MSID,i.e., the MS MAC address is included in the message, it is notified tothe control message generation part 40 to convert the CID field of theheader of the received RNG-RSP message into a CID for IR, and return itto the MS.

The control message generation part 40 responds to instructions from theranging control part 39, to generate the various sorts of controlmessages, and give them to the PDU generation part 41 as transmissiondata. Further, for the purpose of ensuring transmission regions, arequest is made to the MAP information generation and analysis part 36for ensuring the transmission regions. At this time, informationrequired for creating MAP data (a connection ID and so forth) is alsogiven to the MAP information generation and analysis part 36.

The MAP information generation and analysis part 36 uses a broadcast CIDtransferred from the control message extraction part 35, to controldownlink and uplink communication (MMR link) with the BS, according toDL-MAP and UL-MAP obtained from the BS, and also, to generate DL-MAP andUL-MAP according to scheduling which is carried by itself, and transmitthem to the MS with the broadcast CID. In a frame by which the RS 200transmits the MAP data and corresponding data, a preamble is includedthe same as in the BS 300. This is because synchronization should beestablished in the MS.

38 denotes the packet buffer part. Therewith, according to the MAP datagenerated by the MAP information generation and analysis part 36, packetdata is transferred to the PDU generation part 41 for radiocommunication.

41 denotes the PDU generation part, which obtains the MAP data generatedby the MAP information generation and analysis part 36 and data to betransmitted in the region defined by the MAP data from the packet bufferpart 38 and the control message generation part 40, and gives them to anencoding part 41 as the entire transmission data.

42 denotes the encoding part, and 43 denotes a modulation part. Thetransmission data given by the PDU generation part 41 is encoded by theencoding part 42, and modulation processing is carried out by themodulation part 43 such that, user data is transmitted in transmissiontiming and channel generated by the MAP information generation andanalysis part 36. After that, the thus-obtained data is given to atransmission part 44.

44 denotes the transmission part which transmits the given data as aradio signal to the MS or the BS.

[b] Description of Second Embodiment

In the first embodiment described above, the RS 200 itself generates theMAP data, and transmits it to the MS 100. However, in a secondembodiment of the present invention, which will now be described, the BS300 generates the MAP data which the RS 200 transmits to the MS 100, andtransmits it via the MMR link. Thus, the RS 200 transmits the MAP data,having been received from the BS 300, as MAP data which the RS 200itself is to transmit.

Thereby, the RS 200 can leave scheduling processing in the charge of theBS 300, and thus, a processing load of the RS 200 can be reduced,whereby the apparatus of the RS 200 can be miniaturized.

FIG. 9 shows a ranging and basic capability registration sequence forthe MS 100 to start connection with the RS 200.

In comparison with FIG. 1, it is seen that, the MAP data (3), (5) and(11), corresponding to the messages (2), (3) and (8) of FIG. 1, aretransmitted based on the MAP data (2), (4) and (10) (received in thedata regions) given via the MMR link from the BS 300 to the RS 200.

That is, in FIG. 9, a message of (2) is transmitted as (3), a message of(4) is transmitted as (5) and a message of (10) is transmitted as (11).The other messages correspond to those described above for FIG. 1, andthe same processing is carried out therefor.

The operation will be briefly described.

The MS 100 first receives a preamble signal from the RS 200 (1), andestablishes synchronization. It is noted that, at this time, the MS 100does not distinguish between the RS 200 and the BS 300, and thus,recognizes the RS 200 as the BS 300.

The BS 300 generates MAP information such as DL-MAP and UL-MAP which theRS 200 transmits to the MS 100, and the BS 300 transmits it to the RS200 with the use of the basic CID of the RS 200, via the MMR link,through transmission with the data region (2).

The RS 200 which has received the MAP information then uses a broadcastCID to transmit the received MAP information to the MS 100 as DL-MAP andUL-MAP data (3). It is noted that, the contents of (2) and (3) arebasically identical. However, the connection ID is changed. Further,while the message (2) is transmitted via the MMR link with the datatransmission region (i.e., the transmission region defined by the MAPregion), the message (3) is transmitted in the MAP data transmissionregion which the RS 200 carries out transmission. Also, messages (4) and(10) described below, have the same relationship.

After receiving messages such as the DL-MAP, UL-MAP, DCD, UCD and soforth, thus receiving the necessary information, and then receiving theUL-MAP defining a ranging region (5), the MS 100 uses the ranging regiondesignated by the MAP to transmit a ranging CDMA code to the RS 200 (6).Also at this time, the UL-MAP, having been generated by the BS 300, isthen transmitted and relayed by the RS 200.

The RS 200 having received the code, then transmits an RNG-REQ messageto the BS 300 (7), which message includes information indicating thatthe MS 100 exists which requests connection (i.e., a “New MS”indicator), reception information concerning the CDMA code, for example,a frame number and a sub-channel of the reception of the code, a codevalue, a status and so forth, and also, correction values for when thetransmission parameters of the MS 100 should be corrected.

At this time, a “success” status is given when errors in the frequency,reception power level and timing lie within predetermined values, whilea “continue” status is given when the errors exceed the predeterminedvalues. Further, the RNG-REQ message is transmitted with the use of thebasic CID allocated to the RS 200 by the BS 300. Accordingly, the BS 300can determine which RS has received the connection request, from the CIDof the message. It is noted that, in this sequence, the CDMA code forinitial ranging is assumed. However, the same operation is also carriedout in a case where a CDMA code for HO ranging which is used when the MS100 carries out handover from another BS is received.

The BS 300 having received the RNG-REQ refers to storage data of thestorage part for vacant resources of its own or vacant resources of theRS 200, and therefrom, determines whether or not the new MS 100 can beaccepted. Then the determination result is returned to the RS 200 bymeans of an RNG-RSP message (8). In this message, when the new MS 100 isacceptable, in addition to the “New MS” indicator, the “continue”status, the CDMA code reception information and the correctioninformation are included when the status in the RNG-REQ message receivedform the RS 200 is the “continue” status. On the other hand, the“success” status and the CDMA code reception information are includedwhen the status in the RNG-REQ message received from the RS 200 is the“success” status. The RNG-RSP message is then transmitted to the RS 200with the use of the basic CID of the RS 200. On one hand, when the newMS 100 cannot be accepted, an RNG-RSP message including an “abort”status and the CDMA code reception information is generated andtransmitted to the RS 200 with the use of the basic CID of the RS 200.

The RS 200 which has received the RNG-RSP from the BS 300 generates anRNG-RSP in which, the “New MS” indicator is removed when the receivedmessage includes the “New MS” indicator, and transmits the generatedmessage to the MS 100 with the use of a CID for initial ranging (9).

When transmitting the RNG-RSP of the “success” status to the RS 200, theBS 300 generates UL-MAP including CDMA_Allocation-IE to allocate a bandfor the MS 100, to transmit an RNG-REQ message by means of the MAPinformation generation part 21, and transmits it to the RS 200 with theuse of the basic CID of the RS 200 via the MMR link (10).

The RS 200 which has received the UL-MAP including theCDMA_Allocation-IE transmits the message to the MS 100 with the use of abroadcast CID (11).

The MS 100 having received the RNG-RSP adjusts the frequency, receptionpower level and timing according to the correction information includedin the RNG-RSP, when the status is “continue”, and again transmits aranging CDMA code to the RS 200 (not shown). When the status is“success”, the MS 100 refers to the CDMA_Allocation-IE included in theUL-MAP massage, and transmits an RNG-REQ message to the RS 200, whichincludes the MAC address of the MS 100 (MSID) (12).

The RS 200 having received the RNG-REQ from the MS 100 replaces the CIDfor IR included in the header of the message transmitted by the MS 100with the basic CID of the RS 200, and transfers it to the BS 300 (13).

When receiving the RNG-REQ message transferred from the MS 100, the BS300 identifies the RS 200 which has transmitted the message, from theCID (the basic CID of the RS 200) included in the header of the message,and registers it with association to the MAC address of the MS 100included in the payload part and the RS 200. Thereby, it is possible tomanage as to which RS the MS 100 identified from the MAC address belongsto. Then, the BS 300 generates an RNG-RSP including the basic CID andthe primary CID which are the control connection for the MS 100 whichhas transmitted the RNG-REQ message, and returns it to the RS 200 (14).

The RS 200 having received the RNG-RSP including the basic CID and theprimary CID for the MS 100, from the BS 300, changes the CID in theheader of this message into a CID for initial ranging, and transfers itto the MS 100 (15).

The MS 100 having received the RNG-RSP including the basic CID and theprimary CID transmits an SBC-REQ message to the RS 200 for notifying ofa capability of the MS 100 itself (16).

The RS 200 having received the SBC-REQ message from the MS 100 transfersit to the BS 300 (17).

The BS 300 having received the SBC-REQ message from the RS 200 generatesan SBC-RSP massage notifying the MS 100 of a function which each of theMS 100, the RS 200 and the BS 300 can support, from among the supportfunctions of the capability having been notified of from the MS 100, andtransmits it to the RS 200 (18). At this time, in order that the RS 200can recognize what has the support function included in the SBC-RSP, thebasic CID of the MS 100 included in the header of the SBC-REQ message isused as it is, and the BS 300 transmits the SBC-RSP to the RS 200. Asanother method, the basic CID of the RS 200 may be used in the header,and, in the payload, an identifier indicating the MS 100, for example,the MAC address or the basic CID of the MS 100, may be included.Thereby, the RS 200 can determine which MS has the support function.

It is noted that, in a process in which the RS 200 relays the messagesbetween the MS 100 and the BS 300, the information included in themessages may be obtained by the RS 200. For example, the MAC address,the basic CID, the primary CID of the MS 100, and also, the supportfunctions notified of by the SBC-REQ/RSP messages, can be managed notonly by the BS 300 but also by the RS 200.

The RS 200 which has received the SBC-RSP message transfers it to the MS100 as it is (19).

FIGS. 10 through 13 show a processing flow of the RS 200 when receivingthe ranging code from the MS 100, a processing flow of the RS 200 whenreceiving the RNG-REQ from the MS 100, a processing flow of the RS 200when receiving the RNG-RSP from the BS 300 and a processing flow of theBS 300 when receiving the RNG-REQ, respectively.

Further, a block configuration example of the BS 300 in the secondembodiment of the present invention is the same as that of the BS 300 inthe first embodiment described above.

With reference to the block configuration of the BS 300 shown in FIG. 6,as well as the processing flow of FIG. 13, the operation of the BS 300will now be described.

After receiving a message (Yes in S101 of FIG. 13), the BS 300 extractsa control message (RNG-REQ) from the received message, and gives it tothe ranging control part 26.

The ranging control part 26 analyzes the RNG-REQ message, analyzes theCID included in the header of the message, carries out control describedbelow, and requests the control message generation part 25 to generateand transmit an RNG-RSP message.

When the CID is a CID for initial ranging (IR) (No in S102), this meansthat the message corresponds to a ranging request message from the MS100 or the RS 200 belonging to the BS 300, and thus, it is notified tothe control message generation part 25 to generate the RNG-RSP messageincluding the MAC address included in the RNG-REQ, the “success” status,the basic CID and the primary CID when correction of the frequency,transmission power and timing of the MS 100 is not necessary, andtransmit it with CID=IR (S115). When the correction is necessary, it isnotified to the control message generation part 25 to generate theRNG-RSP message including the MAC address included in the RNG-REQ, the“continue” status, and the necessary correction information, andtransmit it with CID=IR (S115).

When the CID is not for IR but is the basic CID of the MS 100 (Yes inS102 and No in S103), periodic ranging of the MS 100 is carried out(S111). The same as the above-mentioned case for IR, it is notified tothe control message generation part 25 to generate the RNG-RSP includingthe contents depending on whether or not the correction is necessary,and transmit it with the use of the basic CID of the RNG-REQ.

When the CID is not for IR but is the basic CID of the RS 200 (Yes inS103), processing to carry out differs according to whether or not a“New MS” indicator is included in the payload part of the RNG-REQmessage.

When the “New MS” indicator is not included (No in S104), processing tocarry out differs according to whether or not the MS MAC address (MSID)exists. When the MS MAC address does not exist (No in S105), periodicranging of the RS 200 is carried out (S111). When the MS MAC addressexists (Yes on S105), the received RNG-REQ message means a messagerelayed by the RS 200 after being transmitted from the MS 100. At thistime, the MS MAC address in the RNG-REQ message and the basic CIDincluded in the header of the RNG-REQ message are managed withassociation to one another (S108), and thus, the RS 200 currentlyconnected from the MS 100 can be identified. Next, it is notified to thecontrol message generation part 25 to generate the RNG-RSP messageincluding the basic CID and the primary CID to allocate to the MS 100,and transmit it with the use of the CID of the basic CID of the RS 200(S112). The association between the MS 100 and the RS 200, as well asthe basic CID and the primary CID of the MS 100, are managed by an MSmanagement table stored in the storage part.

When the “New MS” indicator exists (Yes in S104), it is determinedwhether or not the new MS 100 is acceptable (S106). This determinationcan be made from busy conditions of the respective resources, such asbusy conditions of the radio resources, a busy condition in themanagement table and so forth. When the new MS 100 is acceptable (Yes inS106), it is notified to the control message generation part 25 togenerate the RNG-RSP message including a “success” status and UL-MAPincluding CDMA_Allocation-IE, and transmit it with the use of the basicCID of the RS 200, when the status in the RNG-REQ is “success” (Yes inS107, then, S109 and S113). When the status included in the RNG-REQ isnot “success” (No in S107), it is notified to the control messagegeneration part 25 to generate the RNG-RSP message including the statusfrom the RNG-REQ, and correction values for the transmission parameters,and transmit it with the use of the basic CID of the RS 200 (S114). TheCDMA_Allocation-IE is created based on information concerning the codenotified of by the RNG-REQ. On one hand, when the new MS 100 is notacceptable (No in S106), it is notified to the control messagegeneration part 25 to generate the RNG-RSP message including an “abort”status, and transmit it with the use of the CID, the same as that of theRNG-REQ, to the RS 200 (5110).

With reference to FIG. 14 showing a block configuration of the RS 200,as well as the processing flows of FIGS. 10, 11 and 12, the operation ofthe RS 200 will now be described.

The block configuration of FIG. 14 is basically the same as that of FIG.8. However, since the generation of the MAP information is notnecessary, a MAP information processing part 46 is provided, instead ofthe MAP information generation and analysis part 36 of FIG. 8. The otherparts are the same as those of FIG. 8, and the duplicated description isomitted.

When the ranging code (for initial ranging, handover ranging or such) isreceived from the MS 100 (Yes in S61 of FIG. 10), the code receptionpart 37 determines whether or not correction of the frequency of thereception signal, reception power level and timing is required, andnotifies the ranging control part 39 of its status(success/abort/continue), code reception information, for example, aframe number, sub-channel, code value of the received code and so forth.When the correction is necessary, the correction values to be directedto the MS 100 are also given to the ranging control part 39. Also, thecorrection values may be stored in the storage part.

The control message extraction part 35 extracts the control message(RNG-REQ, RNG-RSP or such) from the received message, gives it to theranging control part 39, and gives the MAP data received from the BS300, and the MAP data received via the data region of the MMR link to betransmitted to the MS 100, to the MAP information processing part 46.

When receiving information from the code reception part 37, the rangingcontrol part 39 notifies the control message generating part 40 togenerate and transmit the “New MS” indicator and the status(success/abort/continue) to the BS 300 with the basic CID of the RS 200(S62, S63 of FIG. 10). When the status is “continue”, the correctionvalues are also notified of to the control message generation part 40.

When receiving the RNG-REQ message from the control message extractionpart 35 (Yes in S71 of FIG. 11), the ranging control part 39 determineswhether or not the header of the message has a CID for initial ranging(S72). When it is the CID for IR (Yes), it is notified to the controlmessage generation part 40 to transmit the message to the BS 300 afterchanging the CID field in the header of the received RNG-REQ messageinto the basic CID of the RS 200 (S73, S75 of FIG. 11). When the CID isnot the CID for IR (No in S72), that is, when the CID is the basic CIDof the MS 100, it is notified to the control message generation part 40to add to the received RNG-REQ message the status and, if necessary, thecorrection information for the frequency, reception power level andtiming, and transmit it to the BS 300 with the basic CID of the MS 100(S74 and S75).

When receiving the RNG-RSP message from the control message extractionpart 35 (Yes in S81 of FIG. 12), the ranging control part 39 firstdetermines whether or not the CID is the CID for initial ranging (S82).When it is the CID for IR (No), the ranging control part 39 carries outinitial ranging processing of the RS 200 (S86). That is, when the MACaddress included in the RNG-RSP is the MAC address of itself, the basicCID and the primary CID in the message are stored in the storage part,and are used for transmission/reception of subsequent control messages.On one hand, when a CID other than the CID for IR is included in themessage (Yes in S82), processing to then carry out differs according towhether or not the “New MS” indicator is included in the message (S83).When the “New MS” indicator is included (Yes), it is notified to thecontrol message generation part 40 to generate an RNG-RSP messageincluding a “success” status and return it to the MS 100 with the CIDfor IR (S88), when the “success” status is included in the message (Yesin S84). When no “success” status is included in the message (No inS84), it is notified to the control message generation part 40 togenerate the RNG-RSP message including the “abort” status and return itto the MS 100 with the CID for IR (S87). On one hand, when no “New MS”indicator is included in the message (No in S83) and, MSID, i.e., the MSMAC address is included in the message (Yes in S85), it is notified tothe control message generation part 40 to convert the CID field in theheader of the received RNG-REQ into the CID for IR, and transmit it tothe MS 100 (S89). When MSID does not exist (No in S85), the RS 200adjusts the frequency, transmission power and timing according to thecorrection information included in the RNG-RSP, as the periodic rangingprocessing of the RS 200 itself (S90).

The MAP information processing part 46 carries out controlling of thePDU generation part 41 for creating the MMR link according to the MAPdata of the BS 300 transferred from the control message extraction part35. Further, it controls the PDU generation part 41 and so forth, fortransmitting the MAP data to be transmitted to the MS 100, which hasbeen received from the BS 300 via the MMR link.

In the second embodiment described above, when the RS 200 receives theranging code from the MS 100, the RS 200 transmits the code receptioninformation to the BS 300. As a result, the BS 300 should not generatethe code reception information, and thus, the processing load of the BS300 is reduced.

Further, in the second embodiment, another MMR link, than thetransmission region of the ranging signal, defined by the MAP datatransmitted to the RS 200 and so forth, belonging to the BS 300, is usedto transmit the code reception information to the BS 300. As a result,collision with the ranging signal of another MS 100, also belonging tothe BS 300, can be reduced.

Further, also in this embodiment, the transmission region defined by theMAP data transmitted by the BS 300 and the transmission region definedby the MAP data transmitted by the RS 200 may have such a relationshipthat they are separated by means of timing, by means of the frequency(sub-channel) or by means of the spread code or such, so that radiocommunication are not obstructed by one another. For this purpose, theBS 300 should generate appropriate MAP data.

[c] Description of Third Embodiment

In a third embodiment of the present invention, degradation in thetransmission efficiency, otherwise occurring due to a fact that a radiocommunication environment between the BS and the RS and a radiocommunication environment between the RS and the MS may not be identicalto one another can be controlled.

It is noted that, in this embodiment, one example of an authenticationsequence is described, which may be carried out subsequent to theranging and basic capability registration sequence described above forthe first and second embodiments.

FIG. 15 shows the authentication sequence which should be preferablycarried out after the end of the ranging and basic capabilityregistration sequence.

In this embodiment, the MS 100 carries out the authentication sequenceafter finishing the ranging and basic capability registration sequence.

First, the MS 100 transmits its own authentication data (for example, anelectronic certificate including the MS's public key) to the RS 200 withthe use of a PKMv2-REQ message (1). In FIG. 15, an example is shown inwhich, in the PKMv2-REQ message, an EAP (Extensible AuthenticationProtocol: RFC2284) packet is encapsulated. It is noted that, at thistime, the primary CID obtained previously is used as the connection ID.Thereby, both of the RS 200 and the BS 300 can easily identify the MS100.

The RS 200 which has thus received the PKMv2-REQ (EAP-transfer) relaysthe message to the BS 300 (2). There, it is not necessary to decryptcipher at the RS.

The BS 300 which has thus received the PKMv2-REQ (EAP-transfer)transfers the electronic certificate to an external server to obtain anauthentication result, and thus, carries out authentication. When theauthentication is succeeded in, an authentication key (AK) to be sharedby the MS 100 and the BS 300 is then generated, and also, to the MS 100,a PKMv2-RSP (EAP-transfer) including the authentication key (AK or aparameter for generating AK) is generated, which is then returned to theRS 200 (3). At this time, preferably, the AK or the parameter forgenerating the AK is encrypted with the use of the public key includedin the electronic certificate of the MS 100. Thereby, only the MS 100itself, which has the corresponding private key, can decrypt, and thus,it is possible to achieve safe transfer of the authentication keyinformation.

The RS 200 which has thus received the PKMv2-RSP (EAP-transfer) relaysthe message to the MS 100 (4). At this time, the RS 200 does not havethe private key, and thus, cannot decrypt the encrypted authenticationkey information.

On one hand, the BS 300 transmits a PKMv2-RSP (key-transfer (AK))including data obtained from encrypting the authentication keyinformation (AK or the parameter for generating AK), to the RS 200, inorder that the authentication key used with the MS 100 is also sharedwith the RS 200 (5). In the encryption, it is preferable to use the key,shared when the RS 200 has carried out the authentication to connectwith the BS 300. The RS 200 stores the authentication key information.

The MS 100 which has thus received the PKMv2-RSP (EAP-transfer) detectsthat the authentication has been succeeded in. In order to establishsecurity association (i.e., an encryption method and so forth) with theBS 300, the MS 100 transmits a PKMv2-REQ (SA-TEK-request) (6). In thismessage, a calculation result (a hash value, for example) obtained frompredetermined calculation (hash calculation or such, for example) beingcarried out on the AK, obtained from the authentication key information,previously obtained the MS 100, and the transmission data, is added. Forexample, a parameter generated from the AK is one argument of a functionF(x), and, a calculation result F(D) is obtained as a result of thetransmission data D being substituted for x. Further, in this message,encryption methods (for example, AES, DES, key length information and soforth) to require, are included.

The RS 200 which has thus received the PKMv2-REQ (SA-TE-request) relaysthe message to the BS 300.

The BS 300 which has thus received the PKMv2-REQ (SA-TE-request)decrypts the cipher, the same as in the previous case, refers to theencryption methods required by the MS 100, selects a encryption methodwhich can be adopted, determines SA configured by the encryption method(for example, key length information) used between the BS 300 and the MS100, and returns the SA information to the RS 200 by means of aPKMv2-RSP (SA-TEK-response) (8). It is noted that, the BS 300 checks asto whether or not the calculation result (hash value) included in themessage agrees with a calculation result obtained from predeterminedcalculation (for example, hash calculation) with the use of theauthentication key (AK or the parameter obtained from AK) which the BS300 itself has (stores) and the reception data. Thereby, the BS 300determines whether or not the message is one from the MS 100 which hasbeen authenticated and thus is authentic. When it is not authentic, theprocessing should be rejected.

The RS 200 which has thus received the PKMv2-RSP (SA-TEK-response)relays the message to the MS 100 (9).

The MS 100 which has thus received the PKMv2-RSP (SA-TEK-response) andthus shares the SA with the BS 300, transmits a PKMv2-RSP (key-request)requesting from the BS 300 an encryption key for encrypting user data,corresponding to the SA, to the RS 200 (10). At this time, the same as(6), the calculation result is added for the purpose of authentication.

The RS 200 which has thus received the PKMv2-REQ (key-request) relaysthe message to the BS 300 (11).

The BS 300 which has thus received the PKMv2-REQ (key-request) generatesan encryption key corresponding to the SA (TEK: Traffic Encryption Key),encrypts it with the use of the shared key shared with the MS 100,includes it in a PKMv2-RSP (key-replay), and transmits the message to RS200 (12). Also at this time, the BS 300 uses the calculation resultadded in the reception message, for the purpose of authentication tocheck as to whether or not the data is one from the MS 100 which isauthentic. Then, when it is authentic, the PKMv2-RSP is transmitted tothe RS 200.

The RS 200 which has thus received the PKMv2-RSP (key-reply) relays themessage to the MS 100 (13).

On one hand, the BS 300 shares the key information (instead of the dataof the key itself, information for identifying the key, a parameter forgenerating the key or such, may be used) with the RS 200. That is, thekey information (in this example, TEK, i.e., the key itself) isencrypted, and a PKMv2-RSP (key-transfer (TEK)) including TEK, i.e., thethus-encrypted key, is transmitted to the RS 200. In the encryption ofthe key, the key shared upon the authentication for the purpose that theRS 200 has connected with the BS 300, is used.

In this case, TEK is used as the shared key. However, this may also beused as another key (private key or such).

Thus, the RS 200 can obtain AK and TEK required for the data,transmitted/received between the BS 300 and the MS 100.

As a result, the RS 200 can decrypt user data (MAC-PDU) received fromthe MS 100 or the BS 300, and further, TEK is used for decrypting thecipher, so that the RS 200 can obtain the transmission data before beingencrypted.

Further, the RS 200 can adjust the data amount by modifying (dividing,combining with other data or such) the transmission data before beingencrypted (plain language), which is obtained from decryption of theencryption.

For example, when the available transmission speed of data via radiobetween the RS 200 and the MS 100 is lower than the availabletransmission speed of data via radio between the BS 300 and the RS 200,the cipher of MAC-PDU is decrypted, and then, the data is divided into aplurality of MAC-PDU. Then, for each of the thus-divided data, MAC-PDUis encrypted with the use of TEK (shared key), and/or, a predeterminedcalculation result (i.e., an authentication calculation result),obtained from each of the thus-divided data and AK, is added, forexample. After that, the data is transmitted one by one (each divideddata being transmitted with a respective one of different frames). As aresult, it is possible to control degradation in the transmissionefficiency, otherwise occurring due to the difference in the radioenvironment. It is noted that, the authentication calculation result maynot be added when the user data is transmitted, but may be added onlywhen the control data is transmitted (the same manner may be appliedalso in the subsequent processing).

On the other hand, when the available transmission speed of data viaradio between the RS 200 and the MS 100 is higher than the availabletransmission speed of data via radio between the BS 300 and the RS 200,MAC-PDU obtained from decryption with the use of TEK is combinedtogether, then the combined result is again encrypted with the use ofTEK, and/or, a predetermined calculation result with the use of AK isadded thereto, and then, is transmitted within one frame. As a result,it is possible to avoid useless transmission, and to allocate thethus-saved resource to another radio communication.

The reason why the cipher decrypted is again encrypted by the RS 200 isas follows: Since, when receiving MAC-PDU from the RS 200, the MS 100tries to decrypt it as one unit, and thus, an error may occur whendecrypting is tried on incomplete data. Especially when the MS 100 doesnot distinguish as to whether it carries out radio communication withthe RS 200 or the BS 300, a trouble may occur when data modification isthus made by the RS 200. The same situation may occur also when data iscombined as mentioned above. Further, as a result of the RS 200checking, with the use of AK, authenticity of the authenticationcalculation result added to the control message transmitted from the MS100 or the BS 300, it is possible to prevent transfer of non-authenticpacket, and thus, it is possible to effectively use the radio resources.

A configuration of a relay station in the third embodiment is shown inFIG. 8.

The above-mentioned message received from the MS 100 or the BS 300 isgiven to the control message generation part 40 after being extracted bythe control message extraction part 35.

The message transmitted to the MS 100 or the BS 300 is generated andtransmitted in such a manner that the control message generation part 40generates a transmission control message based on the received controlmessage which is then given to the PDU generation part 41.

For example, in FIG. 15, the same message may be used between (1) and(2), between (3) and (4), between (6) and (7), between (8) and (9),between (10) and (11) and between (12) and (13). The control messagegeneration part 40 may not encrypt the reception message, may give it asit is to the PDU generation part 41, and thus, may transmit it from thePDU generation part 41.

On one hand, as to the messages of (5) and (14) in FIG. 15, the messageis given to the encryption processing part 45 from the control messageextraction part 35 since it is one for the RS 200, according to the CID.The encryption processing part 45 decrypts the cipher with the use ofthe key shared between the RS 200 and the BS 300, thus obtainsinformation such as AK which is the authentication key information (orthe parameter for generating AK), TEK which is the encryption keyinformation and so forth, and stores them.

When the dividing or combining of the data is to be carried out asmentioned above, the encryption processing part 45 takes thetransmission packet from the packet buffer part 38, decrypts the cipherwith the use of TEK, and then carries out the above-mentioned dividingor combining of the data. The thus-modified data is then again encryptedwith the use of TEK (i.e., encryption in the same type as that in whichthe BS 300 carries out the encryption), and the thus-encrypted data isthen given to the packet buffer part 38. Thus, the data after being thusmodified can be transmitted.

It is noted that, the transmission region is defined by the MAPinformation generation and analysis part 36, corresponding to thethus-modified data, and the data is thus transmitted.

Further, when the authentication data is required, the encryptionprocessing part 45 carries out the predetermined calculation with theuse of AK (or the parameter for AK) which is stored in the same manner,and the transmission data, encrypts the data with the use of TEK, towhich data the calculation result has been added, and then, gives it tothe packet buffer part 38. It is noted that, the authenticationcalculation result added by the MS 100 may be deleted at this time.

It is noted that, when the radio communication system adopts anautomatic repeat request (ARQ) control system, the BS 300 transmits thedata, after adding identification information for each transmission datasuch as a sequence number or such.

In this case, in the RS 200, as a result of the sequence numberencrypted being decrypted, automatic repeat request control can becarried out separately between the RS 200 and the MS 100.

That is, when it is detected by the decoding part 34 that datatransmission is properly carried out from the BS 300 to the RS 200(i.e., it is detected that the reception is carried out properly from adetermination with the use of a CRC check bit added to the data), theencryption processing part 45 decrypts the cipher, and stores thereception data in the packet buffer 38.

Then, when transmitting to the MS 100, the encryption processing part 45of the RS 200 stores, to the data to which the dividing or combining hasbeen carried out as mentioned above, the sequence number separately inthe same format, an then, encrypts it, and returns it to the packetbuffer part 38. Then, the data is transmitted to the MS 100 from thetransmission part 44. Thereby, the automatic repeat request control canbe carried out between the RS 200 and the MS 100. It is noted that, thesequence number added by the BS 300 is deleted. It is noted that, thedata to which the sequence number has been added, i.e., which is thedata before being encrypted, is stored in the encryption processing part45.

That is, when the data received from the RS 200 has an error, the MS 100identifies the data with the use of the sequence number which the RS 200has added, and makes a repeat request to the RS 200. The RS 200 receivesthe repeat request identifying the sequence number from the MS 100 bythe control message extraction part 35, which then notifies theencryption processing part 45 of the corresponding sequence number. Theencryption processing part 45 reads from the storage part the datahaving the sequence number thus notified of, encrypts it with the use ofTEK, and gives the encrypted result to the packet buffer part 38. Thus,data transmission in response to the repeat request to the MS 100 isthus carried out.

Further, when the RS 200 detects that the reception data from the BS 300has an error, the encryption processing part 45 identifies the data fromthe sequence number added by the BS 300, which is obtained fromdecryption, generates a message to notify the BS 300 of the sequencenumber, and gives it to the packet buffer part 38. Thus, transmission ofthe message to the BS 300 is carried out. Thus, it is possible to send arepeat request to the BS 300 for the desired data.

The present invention is not limited to the above-described embodiments,and variations and modifications may be made without departing from thebasic concept of the present invention claimed below.

What is claimed is:
 1. A relay station comprising: a receiver configuredto receive a signal sequence indicating a connection request, the signalsequence being selected from a predetermined signal sequence group whichis used by a plurality of radio terminals, and to measure receptionquality; a control circuit configured to generate a ranging requestmessage indicating that a radio terminal requesting connection existswhen determining that adjustments are not necessary based on thereception quality; and a transmitter configured to transmit the rangingrequest message to a radio base station.
 2. The relay station as claimedin claim 1, wherein: the reception quality is one of timing offset,power offset, or frequency offset.
 3. A radio communication methodcomprising: in a relay station, receiving a signal sequence indicating aconnection request, the signal sequence being selected from apredetermined signal sequence group which is used by a plurality ofradio terminals; measuring reception quality; generating a rangingrequest message indicating that a radio terminal requesting connectionexits when determining that adjustments are not necessary based on thereception quality; and transmitting the ranging request message to aradio base station.
 4. The radio communication method as claimed inclaim 3, wherein: the receipt quality is one of timing offset, poweroffset, or frequency offset.